1. Field of the Invention
This invention relates generally to a gas-insulated switching device, and more particularly to a gas-insulated switching device of the type in which a bus bar-connecting conductor, connecting a gas circuit breaker portion to a main bus bar conductor, is provided within a cylindrical container accommodating the circuit breaker portion.
2. Description of the Prior Art
Conventional gas-insulated switching devices of the type described are disclosed in Japanese Laid-Open (Kokai) Patent Application No. 50-9044 and U.S. Pat. No. 4,241,379.
The switching device disclosed in the above Japanese Laid-Open application is shown in FIG. 7. A plurality of circuit breaker portions 120 are arranged in parallel relation within a cylindrical container 110 in which electrically-insulating gas such as SF.sub.6 is sealed. A lower end 121 of each circuit breaker portion 120 is supported by a dielectric support member 180 through a movable-side conductor 170 extending in the direction of the axis Z of the breaker portion 120. Although not shown, two main bus bars per phase are connected to the side of the cylindrical container 110. Each breaker portion 120 is electrically connected to main bus bar conductors of the corresponding main bus bars by bus bar-connecting conductors 150 and 160 extending radially of the cylindrical container 110, one ends 151 and 161 of the bus bar connecting conductors 150 and 160 being connected respectively to the main bus bar conductors whereas the other ends 152 and 162 thereof are connected to the movable-side conductors 170. Spacers 130 and 140 electrically insulate the main bus bar-connecting conductors 150 and 160 from the container 110, and also hermetically close openings 111 and 112, respectively, to isolate the gas within the container 110 from the gas in the neighbouring section or chamber. In the illustrated example, three breaker portions 120 constituting a three-phase construction are accommodated within the single container 110, and therefore three sets of identical arrangements (one of which is not shown) are provided.
FIGS. 8 to 10 shows the structure of the switching device disclosed in the above-mentioned U.S. Pat. No. 4,241,379. FIG. 8 is a block diagram incorporating an electric circuit. Three circuit breaker portions 220 are provided within a cylindrical container 210 in which electrically-insulating gas is sealed. A current transformer 290 and a grounding switch 310 are connected to one end 221 of the breaker portion 220. A bus bar-connecting conductor 250 extending radially of the cylindrical container 210, as well as a bus bar-connecting conductor 260 extending axially of the cylindrical container 210, are connected to the other end 222 of the breaker portion 220. Main bus bars 311 and 312 are connected to the outer side of the cylindrical container 210 via insulating spacers 230 and 240. A main bus bar conductor 313 is electrically connected to the bus bar-connecting conductor 250 via a disconnect switch 315, and a main bus bar conductor 314 is electrically connected to the bus bar-connecting conductor 260 via a disconnect switch 316. Components such as an insulation leading means or cable termination 318 and a voltage transformer 319 are connected to a side of one end 221 of the breaker portion 220 via a disconnect switch 317. That portion 201 of this gasinsulated switching device 200 corresponding to what is shown in FIG. 7 is shown in FIG. 9 on an enlarged scale.
As can be seen from FIG. 9, the end 222 of the breaker portion 220 is supported by a dielectric support member 280 through a movable-side conductor 270 extending axially of the breaker portion 220, as in the construction of FIG. 7. The main bus bar conductor 313 5 of the main bus bar 311 (one of the dual bus bars) connected through the insulating spacer 230 is electrically connected to the breaker portion 220 by the bus bar-connecting conductor 250 extending radially of the cylindrical container 210, one end 251 of the bus bar-connecting conductor 250 being connected to the main bus bar conductor 313 whereas the other end 252 thereof is connected to the movable-side conductor 270. The main bus bar conductor 314 of the main bus bar 312 (the other of the dual bus bars) connected through the insulating spacer 240 is electrically connected to the breaker portion 220 through the bus bar-connecting conductor 260 extending generally axially of the cylindrical container 210, one end 261 of the bus bar-connecting conductor 260 being connected to the main bus bar conductor 314 whereas the other end 262 thereof is connected to the bus bar-connecting conductor 250. FIG. 10 is a plan view taken along the line X--X of FIG. 9, and in this Figure, three sets of arrangements constituting a three-phase construction are shown as received within the cylindrical container 210.
In the conventional gas-insulated switching device 100 shown in FIG. 7, the bus bar-connecting conductors 150 and 160, which extend horizontally and radially outwardly from the two axially-spaced portions of the movable-side conductor 170 connected to the end 121 of each breaker portion 120, are connected respectively to the two main bus bars of each phase connected to the outer side of the cylindrical container 121. Therefore, the movable-side conductor 170 need to have the axial length larger than the length (in the axial direction Z) required for two sets of main bus bars. As a result, the axial length of the cylindrical container 110 tends increase, so that the size of the gas-insulated switching device is increased.
On the other hand, in the switching device 200 shown in FIG. 9, the bus bar-connecting conductor 260 is bent in such a manner that one end 261 of the bus bar-connecting conductor 260 (the other end 262 of which is electrically connected to a side of one end 222 of the breaker portion 220) is disposed on the side of the other end 221 of the breaker portion 220. Therefore, the axial length of the cylindrical container 210 is reduced, and the gas-insulated switching device 200 can be of a compact size. However, in an open circuit condition of the breaker portion 220, an interelectrodes voltage is applied between the bus bar-connecting conductor 260 and the end portion 221 of the breaker portion 220, and therefore the conductor 260 and the end portion 221 should be spaced a predetermined distance from each other for insulation purposes therebetween. In addition, a certain distance between the bus bar-connecting conductor 260 and the cylindrical container 210, which is required for insulation purposes, must also be taken into consideration. As a result, in the switching device 200, the diameter of the cylindrical container 210 must be increased.